What rotating machine did Leonardo da Vinci design as a possible lift device?

Leonardo da Vinci designed an aerial screw as a possible lift device.

His drawing, generally dated to about 1489, shows a large helical rotor made from reeds, linen, and wire. Leonardo proposed that the screw could rise if rotated rapidly enough, using the same broad idea that later underlies helicopter flight: a rotating surface pushes air downward and produces lift.

The aerial screw was not a working helicopter. Leonardo did not have a suitable lightweight engine, and the materials and human power available in the Renaissance could not provide enough sustained rotation. The design also lacked the control systems and efficient rotor engineering needed for practical flight.

The machine is often called a helicopter precursor because of its vertical-lift concept. It should not be confused with a modern helicopter, which normally uses powered rotors, a stabilizing structure, and controls for pitch, roll, and yaw.